Synthesis of Bulk Nanostructured Al Alloys with Ultra-High Strength and Wear Resistance for Army Applications
Abstract
Synthesis/processing of nanostructured (amorphous or ultra fine grained) materials was studied via various processing routes such as gas atomization, melt spinning, cryomilling, equal-channel angular pressing (ECAP) and conventional consolidation. Microstructures and mechanical properties of both the amorphous powders and consolidated bulk materials were characterized. The amorphous alloy of A185Ni10La5 (at.%) was fabricated in terms of melt-spun ribbons and particularly, gas-atomized powders (<25 micrometers). The kinetics and microstructure evolution during the devitrification process were carefully investigated using DSC, XRD. SEM, TEM, and SAxS. It was found that quenched-in fcc-Al nuclei present in amorphous Al85Ni10La5 powders. Annealing at 235 degrees C leads to growth of the quenched-in nuclei with the grain size stabilized around 10 nm. With increasing annealing temperatures (i.e., at 245 degs C, 250 degs C and 263 degs), the devitrification takes place via eutectic crystallization with a resultant grain size around 20 nm. At the temperatures >283 degs, the devitrification tends to complete in a short time (-5 min), however, this alloy shows excellent thermal stability to resist grain growth. The influence of devitrification, under various annealing temperatures, on mechanical response was studied by nanoindentation technique. Bulk nanostructured materials were synthesized by consolidating the amorphous Al85Ni10La5 alloy powder with 5083 Al alloy powder milled under cryogenic temperature (cryomilling). The addition of cryomilled 5083 Al alloy is to further increase the specific strength for the bulk materials (e.g., >1000 MPa in compression with the density -2.9 g/cc). The bulk nanostructured material also shows high strength at elevated temperatures (i.e., 400 MPa in compression at 200deg). At room temperature the tensile properties were found be lower than the compressive properties and this differential effects should be investigated in the future st7
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 26, 2005
- Accession Number
- ADA435084
Entities
People
- E. J. Lavernia
Organizations
- University of California